Spray guns are widely used in vehicle body repair shops when re-spraying a vehicle that has been repaired following an accident. In the known spray guns, the liquid is contained in a reservoir attached to the gun from where it is fed to a spray nozzle. On emerging from the spray nozzle, the liquid is atomised and forms a spray with compressed air supplied to the nozzle. The liquid may be gravity fed or suction fed or, more recently, pressure fed by an air bleed line to the reservoir from the compressed air line to the spray gun.
Traditionally, the liquid is contained in a rigid pot mounted on the spray gun by engagement of complementary screw threads on the pot and gun. In this way, the pot can be removed for cleaning or replacement. Typically, the pot is secured to the gun empty and has a removable lid by means of which the liquid can be added to the pot while attached to the gun. On completion of spraying, the pot can be removed and the gun and pot cleaned for re-use.
Such screw threaded connection requires the reservoir to be rotated several times, typically at least four or five turns, to engage fully the threads and secure the reservoir in a fluid tight manner. This is time consuming and requires considerable care and dexterity on the part of the user.
Furthermore, the threads on the gun and pot may be damaged by mis-use, for example if an attempt is made to secure a pot having a non-matching thread. Also, on completion of spraying, careful cleaning is required to remove all traces of liquid from the threads to prevent the threads becoming blocked, for example with dried paint, and to prevent cross-contamination with the liquid next sprayed.
Damaged or blocked threads may render the gun unusable requiring the purchase of a new gun. This adds to costs and is inconvenient if time is lost because a spare gun is not to hand to continue spraying. Moreover, cleaning of the threads usually requires solvents that are also used to clean the gun and pot. The use of solvents is undesirable from health and safety considerations and causes problems for disposal of the solvent after use.
These problems can be reduced by employing a bayonet type connection to secure releasably the reservoir to the spray gun by engagement of bayonet type formations on the reservoir and spray gun with a push-twist action requiring less than one complete turn of the reservoir to connect/disconnect the reservoir. Examples of bayonet type formations that can be used to provide a releasable quick-fit connection of this type are disclosed in International Patent Applications No. WO 98/32539 and WO 01/12337 the disclosures of which are incorporated herein.
The mounted position of the reservoir is fixed by the use of screw threads or bayonet formations to secure the reservoir to the spray gun and adjustments to the mounted position cannot be made with the reservoir attached to the spray gun. Typically, the reservoir has an outlet located at one end on the central longitudinal axis of the reservoir and the spray gun has an inlet at the top (gravity feed) or bottom (suction feed) that is located on the central longitudinal axis of the gun.
A system has been developed that allows the reservoir to be re-filled while attached to the spray gun by means of an inlet located at the end of the reservoir adjacent to the outlet as described in International Patent Application No. WO 02/085533 the disclosure of which is also incorporated herein. With this system, access to the inlet when the reservoir is connected to the spray gun may be improved by arranging the outlet from the reservoir to be offset from the central longitudinal axis of the reservoir.
Such offset arrangement of the outlet can, however, result in the reservoir extending to one side of the spray gun when the outlet is connected to the inlet on the spray gun by engagement of screw threads or bayonet formations to secure releasably the reservoir.
Also, in a gravity feed arrangement, the reservoir is connected to an inlet on the top of the spray gun and the offset arrangement of the outlet may position the outlet above the level of liquid in the reservoir when the spray gun is used at different angles, especially when the liquid level reduces. This can have an adverse effect on flow of paint to the outlet especially when a small volume of paint remains in the reservoir. As a result, the spray gun may have to be maneuvered and held in a position that is uncomfortable for the user in order to dispense the final volume of paint.